1. Field of the Invention
The invention is directed to a printer device and to a method for printing on a print medium of the type employable for a number of printing jobs, wherein recording medium such as a letter is supplied to the printer device by a transport device which holds it in a defined position. As used herein, the terms letter, piece of mail or print medium include all types of envelopes or other recording media. Postal matter, file cards, labels or self-adhesive tapes of paper or similar material can be employed as a recording medium. The printer device is particularly provided for printing letters in a postage meter/addressing machine.
2. Description of the Prior Art
Given greater volumes of postal matter, the processing of postal matter such as letters, cards, packages, etc., is usually undertaken by employing two independent printer devices before the delivery to the carrier. The labeling of the postal matter with the address of the consignor and of the recipient generally ensues with a less expensive printer (open system) and independently of the franking. Automatic franking machines print monetary values and therefore must exhibit a high security standard to prevent tampering (closed system). The use of both systems makes the mail processing correspondingly expensive.
German OS 40 37 186 discloses a stand-along addressing printer that works independently of an automatic franking machine. The printout ensues on one or more tapes, such as self-adhesive labels. The mail customers should additionally apply the bar code onto the postal matter in order to be able to automatically sort and distribute mailings. A personal computer containing the address data file is required in order to additionally print the addresses. The Cod data logic (alpha 39) address printer is used in common for the analog writing of the address as well as for the bar code printing, however, franking is not possible with this printer. The device is intended for public institutions such as post offices, etc. Here, the address encoding printer should be coupled with a specific postage meter machine with which the postal matter can be more inexpensively franked. It is uncertain whether the post offices will offer a rebate so that the customers will prefer this system, or whether the customers will continue to utilize a postage stamp for franking mail. A security check is not undertaken when the automatic franking machine is used, to determine whether the intended letter has been correctly addressed or whether another letter, not addressed with the customer's device, is franked. This is because coupling ensues only for the electronic transmission of fee reduction information via interfaces with the automatic franking machine. A check of the letter weight would also still have to be implemented with a scale before the franking. Three difference devices would thus be required, still without assurance that the with the correct postage fee. Moreover, it is not possible to utilize the same printer device for a number of different printing jobs.
German OS 40 18 166 discloses a franking module that prints both data types, i.e. franking data and address data for parts thereof as barcode. This device is arranged in a slot of a slide-in drive module of a personal computer. A detent, up to which the letters are inserted, and a light barrier are provided in the franking module at the end of a delivery chute for the letters. The light barrier activates a holding means for the duration of the printing event that fixes the letter in this position. The printing unit prints vertically downwardly and can be coupled to a tape dispenser for franking the postal matter that deviates from a standard size. A labeling of the letter with addresses and the calling of the franking program by user prompting ensue in conjunction with the personal computer. In the franking, the processor system of the franking module works independently and stores the accounting data. The letter must be introduced in the longitudinal direction into an introduction slot in which, however, only letters having specific, standardized dimensions fit. The device is intended for SOHO employment (soft offices home offices). It is disadvantageous that only letters having a standard size can be labeled and franked in the apparatus and that the printout must ensue on a self-adhesive tape. A high mail volume thus cannot be processed because the printed tapes must be manually glued.
German Utility Model G94 20 734.8 discloses an arrangement for a postage meter machine, wherein a tape with the franking imprint and a second tape with the address can be printed respectively with a separate printer device. The difficulty is thereby avoided of having to move a printer device. The mechanically immobile arrangement of the printer module cannot be arbitrarily adapted to other printing jobs. The tapes must be glued onto a recording medium; this, however, is not recognized as permissible by every mail carrier because tampering cannot be completely precluded.
In all such machines, the print medium is conducted along a printer device and the franking respectively address is printed in one pass.
It is standard to conduct the print carrier along the printer device either lying flat--see, for example, U.S. Pat. No. 5,467,709--or standing on one edge (German PS 25 24 670, U.S. Pat. No. 5,025,386, German PS 196 05 014 and German PS 196 05 015). In any case, it is important that the print medium and the printer device proceed into a defined position relative to one another so that the imprint ensues at the intended location and with adequate quality.
Given horizontal transport, a relatively large seating surface is required in conformity with the largest print medium format being employed, and as a result a correspondingly large standing surface is in turn required for the machines. In the solution according to U.S. Pat. No. 5,467,709, printing is carried out in non-contacting fashion with an ink printer head that is displaceable into a second position in order to print a franking tape. The print head should be moved and thus must be relatively small and light. An ink tank can be arranged directly at the print head and is co-moved with it. If movement to another printing position were to be necessary in order, for example, to print an address, then the ink consumption would be higher and the print head together with the ink tank would have to be replaced more often. The print head must be easily accessible for replacement. Moreover, the print head must be protected against drying out during longer pauses; this, however, is only possible with a cleaning and sealing station that is applied with an exact fit. A third position, which is at a relatively large distance from one of the two printing positions must be assumed for cleaning. Only slow movements are thereby possible. An alternating printing of an address and a franking imprint would be practically possible only at very low speed with such a device.
The letter usually lies against a longitudinal guide plate that includes a conveyor belt. The longitudinal guide plate is provided with a recess adapted to the conveyor belt and with a rectangular recess for the ink print head which has diagonal rows of jets. The conveyor belt, the longitudinal guide plate and the ink print head are arranged over the letter. The letter is conveyed clamped between the driven conveyor belt and resiliently seated pressure rollers. The resiliently seated pressure rollers and a pressure roller resiliently seated in the printing region are arranged under the letter. The spring bias movement of the pressure rollers and of the pressure plate corresponds to the maximum thickness of the letters, which can fluctuate between 0.2 mm and 20 mm. The spring power must be capable of handling the entire weight range of the letters--approximately 20 through 1000 g--and must also allow the letters to lie adequately flat in the region of the recess for the print head. As a result of the clamping, hard parts such as, for example, metal clips in or on documents contained in the postal matter can bulge through the envelope, which leads to the reduction of the distance of the envelope surface from the print head or can even cause damage thereto.
An optimally small distance between the print medium and the ink print head must be adhered to for the non-contacting ink printing method so that splatters have little effect and so that the print medium does not touch the nozzle surface, which would produce smears. The risk of smearing is still present, however, when the letter leaves the region of the recess and then slides along the longitudinal guide plate under forced drive. All of these conditions cannot be adhered to given rapidly changing mixed mail.
German PS 25 24 670 discloses a system for processing outgoing letter mail differing in weight and differing in dimensions, whereby the letters are conveyed on edge along a conveying path. The conveying path has driven roller pairs and a conveyor belt. In the region preceding the franking imprint, the letter is arrested by the conveyor belt operating as a friction belt and is transported over guide rollers to a postage drum or printing drum with a counter-pressure drum. The counter-pressure drum is seated on a movable printing base whose distance from the printing drum can be set in conformity with the thickness of the letter passing through the franking station at the moment. Aside from the fact that printer drums will no longer satisfy the increased demands of the future, the printing base contains a considerable number of moving parts. This requires a correspondingly high energy expenditure in order to overcome the inertia of the masses of the components.
A postage meter machine is also known from U.S. Pat. No. 5,025,386 wherein the letters are conveyed on edge, slightly inclined on a circular conveyor belt. The letters thereby lie against a guide block in which a print window is provided. A thermal printing head is arranged in the printer window so as to be displaceable laterally and in height, with the franking imprint on the letter proceeding line-by-line. The outlay for the adjustment of the thermal print head is substantial. The size of the print window must be adapted to the maximum length and width of the print format. The individual letter is moved up to the print window and is then arrested and pressed against the guide plate or the print window with a pressure plate. The pressure plate is driven by a motor a lever and gear articulation. This is a relatively significant mechanical outlay and the counter-pressure forces which must be exerted for thermal printing are likewise high. After the printing, the letter is released and conveyed further. Clearly, only low letter throughput quotas can be achieved with this intermittent operation. The aforementioned disadvantages when metal parts or other hard parts are contained on the document in the letter again arise due to the clamping.
It is likewise known to incorporate postage meter machines into a system for address and franking printing. For example, U.S. Pat. No. 5,200,903 discloses that address and postage value imprinting be undertaken in a fast printer device, the printer device having two separate print heads or a single print head width, with the entire printing width of the letter being moved correspondingly past the printer device.
Postal machines are also known that, given a non-horizontal letter transport, enable both franking and address printing with two ink jet print heads or with a common ink jet print head behind a guide plate adjustable in position between two recesses (German PS 196 05 014 and German PS 196 05 015). For the version with two ink jet print heads, however, two cleaning and sealing stations and corresponding actuators, sensors, control and ink delivery means must be redundantly implemented.
The mechanism required for the version with one ink jet print head adjustable in position is extremely complicated because, if the sealing is not tightly done, the print head can dry out. Moreover, the problems that were already explained in conjunction with U.S. Pat. No. 5,467,709 can still occur.